This invention pertains to the art of coupling devices and more particularly to an improved controlled phase sequential sealing and gripping device.
The invention is particularly applicable to a tube coupling arrangement and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and may be advantageously employed for other uses in a variety of environments.
The general environment of the present invention is set forth in a series of patents beginning with U.S. Pat. No. 2,484,815 issued Oct. 18, 1949 and incorporated herein by reference. Shown and described in this patent is the basic structure for a tube coupling arrangement employing first and second ferrules captured between a coupling nut and a coupling body, and which are deformed into sealing and gripping engagement with a tubular member received through the ferrules into the coupling body. A female coupling nut is received over an externally threaded region of the coupling body, and when advanced relative to the coupling body, provides the force necessary to deform the ferrules into gripping and sealing relationship with the tubular member. A predetermined relationship of the pitch and thread in the threaded cooperation between these two components is provided. That is, the nature of the threaded cooperation between the coupling body and coupling nut is such that it provides for controlled deformation of the ferrules after finger-tight makeup to a final sealing and gripping position on the tubular member.
Further refinements of this sequential gripping arrangement are set forth in U.S. Pat. Nos. 3,075,793 issued Jan. 29, 1963 to Lennon, et al. and 3,103,373 issued Sept. 10, 1963 to Lennon, et al. The disclosures of both of these patents are also incorporated herein by reference. Although the latter patents are directed to refinements of the concept disclosed in U.S. Pat. No. 2,484,815, the general intent and purpose is essentially unchanged. That is, once the coupling nut has been brought to a finger-tight conditionon t eh coupling body, a predetermined amount of further nut advancement produces axial compressive forces on the ferrules relative to the coupling body and a corresponding deformation of the ferrules into gripping and sealing relationship with the tubular member. At the same time, a first ferrule is driven into sealing engagement with the coupling body.
As illustrated in the foregoing prior patents, first and second counterbores were employed to receive the front and back ferrules, respectively, around the tubular member. The counterbore arrangements were designed and dimensioned so that a rear shoulder of the coupling nut indirectly transferred axial forces to the front ferrule through abutting engagement with the rear ferrule. Predetermined cooperating thread parameters between the coupling body and coupling nut were utilized for various fitting sizes to achieve the desired coupling results. For example, the prior arrangement utilized a 3/4" thread in a one-half inch fitting.
While the couplings disclosed in the above referenced three patents have enjoyed substantial commercial success, it has been observed that increasing the sidewall thickness of the tubing to be coupled has a tendency to produce deformation of the front ferrule radially outwardly to a greater extent than with a tubular member of lesser wall thickness. Because of the greater resistance to radial compressive forces offered by heavy-walled tubular members, the axial force transferred through the rear ferrule has a tendency to deform the front ferrule radially outwardly to such an extend that it may interfere wit the threaded portion of the coupling nut. Such radially outward expansion may thus render disassembly of the fitting extremely difficult, if not impossible. In such a case, it may not be possible to pass the threads on the coupling nut over the deformed front ferrule to achieve complete disassembly.
As a result of the above described circumstances, it has been considered desirable to provide a fitting arrangement that can be utilized with heavy-walled tubular members without encountering the potential for disassembly problems of the type noted. The subject invention meets these needs and others, and provides a coupling device which has increased effectiveness for heavy-walled tubing applications.